Electron discharge device



June 27, 1933. c. (5. SMITH 1,915,959

ELECTRON DI SCHARGE DEVICE Filed April 2, 1929 Patented June 27, 1933 UNITED STATES PATENT OFFICE CHARLES G. SMITH, 0F MEDFORD, MASSACHUSETTS, ASSIGNOR TO RAYTHEON; INC.; 0] CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS ELECTRON DISCHARGE DEVICE Application filed. April 2,

My invention relates to an electron discharge device especially for use as a rectifier or oscillator. In the ordinary rectifier having a thermionic cathode and operating in a vacuum without substantial ionization, it is well known that there is a considerable resistance in the cathode-anode space due to the space charge of the electrons.

In order to neutralize this space charge effect, recourse may be had to several means. Thus gas may be introduced to furnish positively charged ions in the inter-electrode space resulting from the bombardment of the gas particles by electrons. The positive charge of the ions thus created serves to neutralize the negative charge of adjacent electrons and thus allows a more dense stream of electrons without increasing the potential necessary to draw the electrons to the anode. Another method isby having a. positively charged electrode in the space between the cathode and anode, and magnetic means to prevent the electrons from flowing to this positively charged member. Thus while the electronic repulsive forces are neutralized in a greater or less degree by the positively charged member, most of the current continues on to the anode.

This latter method is objectionable in that only a comparatively small degree of space charge neutralization maybe successfully obtained.

An object of my invention is to obtain more effective space charge neutralization while at the same time, allow the normal cathodeanode current flow. A further object is to secure the above objects by simple and efiicient apparatus. Another object is to obtain oscillatory currents of considerable magnitude from my invention. Further objects will occur to those skilled in the art.

Referring to the drawing, Figure 1 is a sectional elevation of a tube embodying my invention.

Figure 2 is a view showing the tube of Figure 1 in a circuit for producing osc1llations.

Referring to the drawing, 1 1s a glass or other insulating container having reentrant presses 2, 3, and 4. Press 2 has sealed there- 1929. Serial No. 351,999.

in two wires 5 and 6 supporting a thermionic cathode 7 therebetween. A suitable transformer 8 is connected to wires 5 and 6 for energizing filament 7. Press 3 has wires 10 and 11 sealed therein. These wires support a cylindrical anode 12 positioned around. cathode 7. Press 4: has wires 14: and 15 sealed therein which support a cylindrical member 16 between cathode 7 and anode 12. Member 16 is preferably made of very thin metal such as nickel or beryllium and may be perforated if desired.

Anode 12 through supporting wires 10 and 11 is connected through a source of alternating current 20 to a load L to filament 7. Member 16 is connected through its supporting wires 1 1 and 15 to a source 21 in series with 20 and capable of charging member 16 to a higher positive potential than member 12 and in phase therewith. The operation of this rectifier is as follows. Electrons emitted by filament 7 are drawn to member 16 assuming that 16 and 12 are both positive to 7. If the positive wave happens to be just rising from zero value, the potential at 12 will be comparatively low and the potential at 16 will be a little higher. Under these conditions, practically the entire space current at that instant will go from 7 to 16 and around through the outside circuit. As soon as the potential goes up, 16 is at a high potential compared to the potential of 12. Thus l6 may well be at a potential of around 150,000 volts while 12 may be at around 100 or even less. .Under these conditions, electrons will be drawn from 7 to 16 with great force. The speed of the electrons on arriving at 16 will be so reat that they will penetrate member 16 and keep on traveling. Of course if member 12 were not at a higher potential than 7, it is evident that as the electrons went further from 16 their speed would be reduced to zero and they would finally return to 16. However,

because member 12 is positively charged and is positioned sutficiently close to member 16, electrons penetrating member 16 will go to' member 12 and complete the circuit in this manner. Since electrons travel slowly when striking the anode, losses will be low.

The very large stream of electrons emitted from 7 are condensed into a compact stream by the influence'of the positive charge of member 16. Evidently considerable of the space charge existing in the space between cathode and anode is neutralized by the pres ence of the positive charge on 16. tive resistance of the tube is therefore materially reduced. The drop between cathode and anode is greatly reduced and a large space current is possible. Practically all of the emitted electrons go on through member 16 to 12. Hence, there is but very little current between the cathode and control member or neutralizing member 16.

A tube of this character may be adapted for producing electrical oscillations of great current intensity. From a low voltage in which practically all the current is between cathode 7 and member 16 to a high voltage where practically all the current is between cathode 7 and anode 12, it is evident that the outside circuit connecting cathode 7 to member 16 has a negative characteristic. A tube of this character is shown in Figure 2 connected to produce oscillations. In this tube, electrodes 12 and cathode 7 are supported by wires 5, 6, 10, and 11, sealed into one press 2. Between anode 12 and cathode 7 a suitable battery or source of direct current 25 is connected with the positive pole to the anode. Another battery 26 is connected between the cathode 7 through an oscillating circuit 27 to control or neutralizing electrode 16. Battery or direct current source 26 furnishes a very much higher potential than 25. Transformer 24 energizes cathode 7. \Vith the circuit closed and the cathode emitting electrons, it is evident that the voltage between cathode 7 and electrode 16 will rise. ,The current increases also at this time. The voltage soon rises to a value which is sufficiently high to draw electrons through 16 and cause the space current to go between cathode 7 and anode 12. Under these condi tions. it is evident that the current in circuit 7, 26, 27 and 16 will go down to a very low value. Thus this circuit has a negative characteristic in that as the voltage rises, the current falls. Oscillating circuit 27 connected as shown, takes advantage of this characteristic to cause the device to act as an oscillator.

gara es An oscillator of this type can be operated at high efiiciency with very simple connections.

I claim:

1. A space discharge device comprising, an evacuated vessel, a cathode and a cooperating anode spaced apart from each other in said vessel, and an intermediate solid electrode obstructing the path of electrons between said cathode and said anode, said intermediate electrode being of a sufliciently small thickness and of a material permitting passage of electrons therethrough under the application thereto of a high 'positive potential with respect to the cathode, and means for maintaining said intermediate electrode at a high positive potential greater than the anode at which electrons from the cathode acquire a high velocity sufficient to cause said electrons to penetrate through the solid body of said intermediate electrode and to continue to travel towards said anode and sustain an electron flow from said cathode to said anode.

2. A space discharge device comprisin an evacuated vessel, a thermionic catho e and an anode maintained at a positive potential with respect to said cathode, and an intermediate solid electrode obstructing the path of electrons between said cathode and said anode, said intermediate electrode being of a sufiiciently small thickness and of a material permitting passage of electrons therethrough under the application thereto of a high positive potential with respect to the cathode, said intermediate solid electrode being maintained at a high positive potential greater than the potential of said anode at which electrons from the cathode are accelerated by said intermediate anode to a high velocity sufficient to cause said electrons to penetrate through said intermediate solid electrode and to continue to travel to said anode, thereby producing a space discharge between said cathode and said anode while maintaining the electron current to said intermediate electrode negligible compared to the current to said anode.

In testimony whereof, I have signed my name to this specification.

CHARLES G. SMITH.

ICC; 

